Amy and Rory's Christmas honeymoon is interrupted when their spaceship suddenly plummets through a maelstrom of fog towards a crash landing on the planet below. Miserly Kazran Sardick possesses a machine which can control the fog, but when the Doctor implores him to save the doomed vessel, he refuses. Determined to rescue not only his friends but all four thousand people aboard the ship, the Doctor travels back in time on a mission to change Kazran's life for the better... but only if he can navigate the shoals of bitterness and heartbreak which have made Kazran the man he is today.

During Russell T Davies' time as Doctor Who's executive producer, a Christmas special had become an annual tradition. It began with David Tennant's first full story as the Tenth Doctor, The Christmas Invasion, in 2005 and culminated with the first part of his final adventure, The End Of Time, in 2009. On March 18th, 2010, it was announced that the holiday specials would continue under Davies' successor, Steven Moffat. In fact, around the same time, a director was already being lined up for the 2010 edition. This would be Toby Haynes, who was just finishing work on the Season Thirty-One finale, The Pandorica Opens / The Big Bang.

Meanwhile, Moffat had begun to formulate ideas for his first Christmas special. He wanted to put a Doctor Who spin on his favourite yuletide story: Charles Dickens' 1843 novel A Christmas Carol. Although it had previously been the inspiration for 1986's The Trial Of A Time Lord, that serial had utilised only the basic framework in which events were depicted from an individual's past, present and future. Moffat wanted to directly tackle the book's redemption of the parsimonious Ebenezer Scrooge, with the Doctor taking the role of the Spirits of Christmas Past, Christmas Present and Christmas Yet To Come. Indeed, the special would ultimately be called A Christmas Carol.

Grounded in Los Angeles, Steven Moffat set to work on his script for A Christmas Carol

In April, Moffat was in the United States on a promotional junket with Matt Smith and Karen Gillan when the Eyjafjallajökull volcano in Iceland erupted, throwing international air traffic into chaos. Grounded in Los Angeles, Moffat set to work on his script for A Christmas Carol. Given that his surroundings were anything but wintry, he initially struggled to put himself in the right frame of mind. Eventually, Moffat downloaded a playlist of seasonal tunes and cranked up the air conditioning to approximate Christmas as best he could. He completed his first draft on May 3rd.

A Christmas Carol would not be the first time that Moffat had portrayed the Doctor changing somebody's personal history as a means to an end. This had also been the basis of “Continuity Errors”, a Seventh Doctor short story he had written for the 1996 anthology Decalog 3: Consequences from Virgin Books. In addition to Dickens' A Christmas Carol, Moffat's other primary inspiration was his own childhood dread that sharks might leave the water and climb onto the land, a nightmare fuelled by the 1975 blockbuster horror film Jaws. A Christmas Carol would stand apart from the ongoing story threads Moffat had woven -- but not resolved -- throughout Season Thirty-One, and so the narrative's emphasis was placed firmly on the Doctor. Amy and Rory were largely confined to the spaceship Thrasymachus, which was named for an ancient Greek orator. The vessel originally carried four hundred and three passengers and crew, rather than four thousand and three.

During the break following the end of recording on Season Thirty-One, a number of changes took place in the Doctor Who production office. Three individuals had been sharing the producer's role over the past year, with Tracie Simpson and Peter Bennett alternating throughout the season, and line producer Patrick Schweitzer seconding Simpson for two episodes recorded in Croatia. However, all three had now moved on to other projects: Simpson became the line producer on Baker Boys and Casualty, Bennett would next work as a production manager on Casualty and as a first assistant director on Sherlock, and Schweitzer joined The Hour as its line producer. Coming aboard Doctor Who on an interim basis was Sanne Wohlenberg, who had previously produced Funland, The Whistleblowers and Wallander.

Another new face amongst the crew was Michael Pickwoad, who was taking over as production designer from Edward Thomas. Having been part of the Doctor Who team since the programme's return in 2005, Thomas had departed during the latter part of Season Thirty-One, after which Tristan Peatfield had filled in for the final recording block. Pickwoad's extensive resume included the 1987 cult classic Withnail & I, plus the 2009 remake of The Prisoner. His father was actor William Mervyn, who had appeared in 1966's The War Machines.

Steven Moffat and Toby Haynes were impressed with Katherine Jenkins' talent and enthusiasm

Cast in the key role of Kazran Sardick was three-time Laurence Olivier Award winner Michael Gambon. On television, he had starred in programmes such as The Singing Detective and Maigret, while his films included Gosford Park and The King's Speech. He had also succeeded Richard Harris as Hogwarts headmaster Albus Dumbledore in the Harry Potter movies. A significant challenge was finding someone to play Abigail Pettigrew, given the fact that the story's climax would hinge upon her singing ability. An early idea was for the actress to mime along to a vocal track, perhaps provided by popular classic/contemporary singer Katherine Jenkins. A native of Neath in Wales, Jenkins had first captured the spotlight in 2003, when she sang for Pope John Paul II at Westminster Cathedral. It was then suggested that Jenkins might be interested in actually appearing as Abigail. Although she was not a trained actress, Moffat and Haynes were impressed with Jenkins' talent and enthusiasm during a meeting on June 28th. They decided to offer her the role, which she nervously accepted.

Three and a half months had elapsed between the end of production on Season Thirty-One and the start of work on A Christmas Carol. In the interim, Smith had also appeared as the Doctor in Death Of The Doctor for the fourth season of the spin-off series The Sarah Jane Adventures. Recording for the festive special began at Mir Steel in Newport, where scenes in the Sardicktown streets were filmed from July 12th to 15th; on the last day, Haynes also shot material in Isabella's home. This work included the climactic scene where Abigail's song saved the Thrasymachus. The creation of Murray Gold, who regularly composed Doctor Who's incidental music, Silence Is All You Know was his first original song for a Christmas special since 2007's Voyage Of The Damned. The week ended at Doctor Who's regular studio facilities in Upper Boat, where scenes aboard the Thrasymachus were taped on July 16th and 17th. The design of this set was intentionally reminiscent of the bridge of the various starships Enterprise from the Star Trek franchise.

After a day off on Sunday the 18th, most of the ensuing week was spent at the Coal Exchange in Cardiff Bay. From July 19th to 22nd, it was the venue for scenes in Kazran's bedroom, including the closet and the rooftop outside the window. Also filmed on the last day were Abigail's recorded message and the sequence of the little girl spotting the shark-drawn rickshaw, before cast and crew relocated to Wrinstone House in Wenvoe, which posed as Frank Sinatra's estate. Then it was back to Upper Boat on July 23rd for various effects shots -- notably those involving the rickshaw -- before a break over the weekend.

The following week was confined to Upper Boat, with the chief focus from July 26th to 31st being the scenes in Kazran's main room. The enormous scale of the set, with its oversized fireplace, was inspired by Xanadu, the mansion built by newspaper magnate Charles Foster Kane in Orson Welles' 1941 movie classic Citizen Kane. The portraits of Elliot Kazran and Abigail Pettigrew were painted by Pickwoad's daughter, Katie. Part of the 29th was spent on more rickshaw footage, while several inserts were on the agenda for the 31st.

The production of A Christmas Carol stood down on Sunday, August 1st, before Haynes' team returned to Upper Boat on the 2nd for scenes in the TARDIS, as well as the remaining rickshaw material. The rest of the week -- from August 3rd to 6th -- saw part of the Johnsey Estates in Pontypool's Mahilad Park Industrial Estate transformed into the cryo-cave. One more day of recording was scheduled there after the weekend, on August 9th. This marked the end of principal photography, although some new and alternative shots of Amy and Rory on the Thrasymachus bridge were later completed at Upper Boat on October 8th. Meanwhile, there would be a four-week break before Season Thirty-Two went before the cameras.

A Christmas Carol was the first Doctor Who episode transmitted on the new BBC One HD channel, which had launched on November 3rd. While the programme had been available in high definition since 2009's Planet Of The Dead, broadcasts in the higher-resolution format were previously housed on BBC HD, which featured programming from across the BBC spectrum. The new channel ensured that Doctor Who would henceforth be televised simultaneously in both standard and high definition, avoiding the sort of delay in the high-definition broadcast which had impacted Season Thirty-One's Victory Of The Daleks.

The transmission of A Christmas Carol on Christmas Day eclipsed The Eleventh Hour as the most-watched Eleventh Doctor story to that point. In fact, during the remainder of Smith's tenure, only the fiftieth-anniversary special The Day Of The Doctor in 2013 would attract more viewers. Unlike previous dips in Doctor Who's ratings, however, this was less suggestive of a decrease in the show's popularity than it was an indication of the evolving media landscape. Slowly but surely, new ways of accessing content -- such as the BBC's own iPlayer service -- were forever changing the face of television.

• Doctor Who Magazine Special Edition #29, 14th December 2011, “A Christmas Carol” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #66, 2017, “Story 213: A Christmas Carol”, edited by John Ainsworth, Hachette Partworks Ltd.